A search engine is a computer program that enables people to type in keywords or phrases and retrieve information based on those terms. The purpose of a search engine is to find the most relevant information based on a set of criteria, including quality and relevance. Search engines have primary goals, such as making money and collecting data about searchers, but also have secondary goals such as ensuring that users get the most accurate information possible based on their queries.

A key part of a search engine is an algorithm, which is a complex mathematical formula that determines the order of results for a particular query. The algorithm is a closely guarded secret, but there has been a substantial industry developed around trying to manipulate it in order to obtain high rankings on a search engine results page (SERP). This is known as Search Engine Optimization or SEO.

The first step in search engine technology is a program called a crawler that is sent out to scour the web, looking for webpages to index. Once it finds a suitable webpage, the crawler will follow links on that page to find more pages and then add them to its cached database of found URLs, which is called an index.

Once the index is built, the search engine will start searching it for information matching a specific request. It will then rank the results in a particular order based on its interpretation of what it thinks is most important to the user. The algorithm takes into account a wide variety of factors, including keyword density, page authority and popularity, to come up with the ranking. Different search engines have slightly different algorithms, so a high ranking on one does not guarantee a top ranking on another.

You can narrow down your search results by using search engine techniques such as truncation and filtering. Truncation involves putting a special symbol, such as an asterisk or the letter “*” around a search word or phrase to enable the search tool to look for all words that have that base or trunk, regardless of what letters appear afterward. This is helpful when you want to broaden your search but need to include certain words in it.

By combining two or more keywords with the OR operator, you can narrow down your results. When you use OR, your search engine or subject database will only look for information that features either of the keywords in question, significantly reducing your number of results. To exclude a particular keyword, you can use the NOT operator; however, this should be done with caution as it may result in eliminating a lot of pertinent information.

Another useful search technique is a modifier, such as minus or site, that can be applied to a search to limit it to information on a certain website. This can help you avoid sites with spam content or inappropriate links, which may harm your results.